Interpretive Summary: Cognitive impairment in dialysis is an increasingly important public health problem given the aging end-stage renal disease population and the increasing prevalence of diabetes and vascular disease, but there are few detailed data on cognition in patients undergoing dialysis treatment. We evaluated the frequency of and risk factors for poor cognitive performance using detailed neurocognitive testing. In this cross-sectional cohort study, 314 hemodialysis patients from 6 Boston-area hemodialysis units underwent detailed cognitive assessment. Tests were given to patients that assessed a broad range of cognitive function. All statistical analyses were adjusted for age, sex, race, and education status. Compared with the general population, patients on dialysis had significantly poorer executive function (e.g. planning, psychomotor speed, and mental flexibility), but not memory performance. In adjusted analyses, vascular risk factors (such as diabetes, hypertension, and smoking) and vascular disease were associated with lower executive function. The findings of this research suggest that targeting lifestyle behaviors, including nutrition and exercise, that are risk factors for vascular disease may also help to improve cognitive function in these patients.

Technical Abstract:
There are few detailed data on cognition in patients undergoing dialysis. We evaluated the frequency of and risk factors for poor cognitive performance using detailed neurocognitive testing. In this cross-sectional cohort study, 314 hemodialysis patients from 6 Boston-area hemodialysis units underwent detailed cognitive assessment. The neuropsychological battery assessed a broad range of functions, with established age-, sex-, and education-matched normative scores. Principal component analysis was used to derive composite scores for memory and executive function domains. Risk factors for each domain were evaluated using linear regression adjusting for age, sex, race, and education status. Analyses were repeated in those with Mini-Mental State Examination (MMSE) score greater than or equal to 24. Compared with population norms, patients on dialysis had significantly poorer executive function but not memory performance, a finding that persisted in the subgroup with MMSE score = 24. In adjusted analyses, vascular risk factors and vascular disease were associated with lower executive function (p < 0.01). There is a high frequency of poor cognitive performance in hemodialysis patients, primarily affecting executive function. Risk factors for worse executive function include vascular risk factors as well as vascular disease. Normal performance on the MMSE does not preclude impaired cognitive function, because individuals with MMSE score = 24 also have a high frequency of poor cognitive performance.